Engine balancer system

ABSTRACT

An engine balancer system is provided in which a balancer housing ( 17 ) disposed so as to face an oil pan beneath a crankshaft is formed by joining an upper housing ( 29 ) and a lower housing ( 30 ) via mating faces (P), and the height of the mating faces (P) is lower on a vehicle front side than on a vehicle rear side. Oil discharge holes ( 45   a   , 46 ) for discharging oil that is within the balancer housing ( 17 ) are formed in the mating faces (P) on the higher side of the balancer housing ( 17 ) and in the upper housing ( 29 ) above the mating faces (P) on the lower side of the balancer housing ( 17 ). This enables the position of the oil discharge hole ( 45   a ) on the lower side to be as high as possible, thereby suppressing penetration of oil into the interior of the balancer housing ( 17 ) through the oil discharge hole ( 45   a ).

RELATED APPLICATIONS

This is a continuation application U.S. Ser. No. 11/900,967 filed Sep.14, 2007, which is a continuation of U.S. Ser. No. 11/407,620, filedApr. 20, 2006, now U.S. Pat. No. 7,270,104 B2, which is a continuationof U.S. Ser. No. 10/507,464, filed May 31, 2005, now U.S. Pat. No.7,047,927 B2, which is a 35 U.S.C. 371 national stage filing ofInternational Application PCT/JP03/02765 filed Mar. 10, 2003, whichclaims priority to Japanese Patent Application No. 2002-64877, filedMar. 11, 2002, the contents of which are incorporated herein byreference.

FIELD OF THE INVENTION

The present invention relates to an engine balancer system having abalancer housing formed by joining an upper housing and a lower housingvia mating faces, the balancer housing being disposed so as to face anoil pan beneath a crankshaft of an engine.

BACKGROUND ART

Such an engine balancer system is known from Japanese Patent ApplicationLaid-open No. 2001-140985.

In this conventional balancer system, a balancer housing is formed byjoining an upper housing and a lower housing, and oil within thebalancer housing is discharged via oil discharge holes formed in matingfaces of the two housings.

If an engine is mounted in a vehicle body with its cylinder axisinclined, since the mating faces of the upper housing and the lowerhousing of the balancer housing are also inclined, when oil within anoil pan is agitated there is a possibility that oil might penetrate intothe interior of the balancer housing via an oil discharge hole formed inthe mating faces on the lower side.

DISCLOSURE OF INVENTION

The present invention has been achieved under the above-mentionedcircumstances, and it is an object thereof to suppress the penetrationof oil into the interior of the balancer housing via the oil dischargehole even when the balancer housing is provided at an inclinationrelative to the horizontal direction.

In order to attain this object, in accordance with a first aspect of thepresent invention, there is proposed an engine balancer system having abalancer housing formed by joining an upper housing and a lower housingvia mating faces, the balancer housing being disposed so as to face anoil pan beneath a crankshaft of an engine, and the balancer housingbeing inclined so that the height of the mating faces varies from oneside to the other, wherein oil discharge holes for discharging oil thatis within the balancer housing are formed in the mating faces on thehigher side of the balancer housing and in the upper housing above themating faces on the lower side of the balancer housing.

In accordance with this arrangement, since the oil discharge holes fordischarging the oil that is within the balancer housing are formed inthe mating faces of the upper housing and the lower housing on thehigher side of the balancer housing and in the upper housing above themating faces on the lower side of the balancer housing, oil can easilybe discharged on the higher side of the balancer housing, and by settingthe oil discharge hole on the lower side of the balancer housing at ashigh a position as possible, it is possible to suppress the penetrationof oil into the interior of the balancer housing via the oil dischargehole.

Furthermore, in accordance with a second aspect of the presentinvention, in addition to the first aspect, there is proposed the enginebalancer system wherein an angle between the lower housing and themating faces on the lower side of the balancer housing is larger than anangle formed between the lower housing and the mating faces on thehigher side of the balancer housing.

In accordance with this arrangement, since the inclination of the lowerhousing is shallow on the higher side of the balancer housing where itis difficult for oil to be discharged via the oil discharge hole, itbecomes easy for oil to be discharged via the oil discharge hole, andsince the inclination of the lower housing is steep on the lower side ofthe balancer housing where it is easy for oil to be discharged via theoil discharge hole, it is possible thereby to contribute to a reductionin the dimensions of the balancer housing.

Moreover, in accordance with a third aspect of the present invention, inaddition to the first or second aspect, there is proposed the enginebalancer system wherein the engine is mounted transversely with thecrankshaft disposed along the lateral direction of a vehicle body, thehigher side of the balancer housing faces the rear of the vehicle body,and the lower side of the balancer housing faces the front of thevehicle body.

In accordance with this arrangement, since the engine is mountedtransversely and the higher side and the lower side of the balancerhousing face the rear and the front of the vehicle body respectively, itis possible, due to the oil level tilting when the vehicle isaccelerating forward, to discharge oil from the oil discharge hole onthe higher side of the balancer housing, where it is difficult for oilto be discharged, thereby improving the forward acceleration performanceof the vehicle.

Furthermore, in accordance with a fourth aspect of the presentinvention, in addition to any one of the first to the third aspects,there is proposed the engine balancer system wherein a baffle plateextending from a position lower than the mating faces to a higherposition is provided in the lower housing on the higher side of thebalancer housing.

In accordance with this arrangement, since the baffle plate extendingfrom the position lower than the mating faces to the higher position isprovided on the higher side of the balancer housing where the oildischarge hole is provided in the mating faces of the upper housing andthe lower housing, even when the oil level within the oil pan isdisturbed it is possible to prevent the oil from penetrating into theinterior of the balancer housing via the oil discharge hole formed inthe mating faces.

Moreover, in accordance with a fifth aspect of the present invention, inaddition to the first aspect, there is proposed the engine balancersystem wherein the engine is mounted transversely with the crankshaftdisposed in the lateral direction of a vehicle body, the lower side ofthe balancer housing faces the rear of the vehicle body, and the higherside of the balancer housing faces the front of the vehicle body.

In accordance with this arrangement, since the engine is mountedtransversely, the lower side of the balancer housing faces the rear ofthe vehicle body, and the oil discharge hole is formed in the upperhousing above the mating faces on the lower side of the balancerhousing, it is possible to suppress the penetration of oil into theinterior of the balancer housing via the oil discharge hole even whenthe oil level is tilted while the vehicle is accelerating forward,thereby suppressing any degradation in the forward accelerationperformance of the vehicle.

Furthermore, in accordance with a sixth aspect of the present invention,in addition to the first aspect, there is proposed the engine balancersystem having the balancer housing facing the oil pan disposed beneaththe crankshaft and having an oil discharge hole for discharging oil thatis within the balancer housing formed in an upper face of the balancerhousing, wherein the position of an oil outlet at the lower end of anoil return passage formed in an engine block and the position of the oildischarge hole of the balancer housing are displaced from each other.

In accordance with this arrangement, since the position of the oiloutlet at the lower end of the oil return passage and the position ofthe oil discharge hole of the balancer housing are displaced from eachother, it is possible to suppress the flow of oil, which has beendischarged from the oil outlet of the oil return passage, into theinterior of the balancer housing through the oil discharge hole of thebalancer housing.

Moreover, in accordance with a seventh aspect of the present invention,in addition to the sixth aspect, there is proposed the engine balancersystem wherein the oil discharge hole of the balancer housing is coveredby a baffle plate, and the oil outlet of the oil return passage isdisposed at a position that avoids the baffle plate.

In accordance with this arrangement, since the oil discharge hole of thebalancer housing is covered by the baffle plate, it is possible toprevent oil from flowing into the interior of the balancer housing viathe oil discharge hole. Moreover, since the oil outlet of the oil returnpassage is disposed at the position that avoids the baffle plate, it ispossible to smoothly return to the oil pan the oil discharged via theoil outlet without interference from the baffle plate.

Furthermore, in accordance with an eighth aspect of the presentinvention, in addition to the seventh aspect, there is proposed theengine balancer system wherein an escape section is formed in the baffleplate, the escape section letting the oil discharged via the oil outletof the oil return passage escape.

In accordance with this arrangement, since the escape section lettingthe oil discharged via the oil outlet of the oil return passage escapeis formed in the baffle plate, it is possible by bringing the oil outletcloser to the baffle plate to suppress any increase in the dimensions ofthe engine, and to suppress interference by the baffle plate with theoil discharged via the oil outlet.

Moreover, in accordance with a ninth aspect of the present invention, inaddition to the eighth aspect, there is proposed the engine balancersystem wherein the escape section is formed between fastening parts viawhich the baffle plate is secured.

In accordance with this arrangement, since the escape section of thebaffle plate is formed between the fastening parts via which the baffleplate is secured, it is possible to suppress any degradation in therigidity of the fastening parts.

Furthermore, in accordance with a tenth aspect of the present invention,in addition to the ninth aspect, there is proposed the engine balancersystem wherein an edge of the escape section of the baffle plate is bentdownward.

In accordance with this arrangement, since the edge of the escapesection of the baffle plate is bent downward, it is possible to smoothlyguide the oil discharged via the oil outlet of the oil return passage tothe oil pan and, moreover, improve the rigidity of the baffle plate.

A lower block 14 of embodiments corresponds to the engine block of thepresent invention, bolts 32 and 50 of the embodiments correspond to thefastening parts of the present invention, and first to third baffleplates 47 to 49 of the embodiments correspond to the baffle plate of thepresent invention.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 to FIG. 13 illustrate a first embodiment of the presentinvention;

FIG. 1 is a front view of an engine,

FIG. 2 is a sectional view along line 2-2 in FIG. 1,

FIG. 3 is a sectional view along line 3-3 in FIG. 2,

FIG. 4 is a sectional view along line 4-4 in FIG. 2,

FIG. 5 is a sectional view along line 5-5 in FIG. 3,

FIG. 6 is a view from arrowed line 6-6 in FIG. 2,

FIG. 7 is a view from arrowed line 7-7 in FIG. 2,

FIG. 8 is a sectional view along line 8-8 in FIG. 6,

FIG. 9 is a sectional view along line 9-9 in FIG. 6,

FIG. 10 is a sectional view along line 10-10 in FIG. 6,

FIG. 11 is a sectional view along line 11-11 in FIG. 6,

FIG. 12 is a sectional view along line 12-12 in FIG. 6, and

FIG. 13 is an enlarged view of a part 13 in FIG. 7.

FIG. 14 is a view, corresponding to FIG. 13, of a second embodiment ofthe present invention.

FIG. 15 is a view, corresponding to FIG. 3, of a third embodiment of thepresent invention.

FIG. 16 to FIG. 19 illustrate a fourth embodiment of the presentinvention; FIG. 16 is a view corresponding to FIG. 3, FIG. 17 is asectional view along line 17-17 in FIG. 16, FIG. 18 is a view from thereverse side of FIG. 17, and FIG. 19 is a sectional view along line19-19 in FIG. 17.

FIG. 20 is a view, corresponding to FIG. 19, of a fifth embodiment ofthe present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

A first embodiment of the present invention is explained below withreference to FIG. 1 to FIG. 13.

As shown in FIG. 1, an outer shell of a vehicular four cylinder inlineengine E is formed by stacking, from the top to the bottom, a head cover11, a cylinder head 12, a cylinder block 13, a lower block 14, and anoil pan 15. A crankshaft 20 is disposed along the lateral direction ofthe vehicle body, and a cylinder axis L is inclined toward an exhaustside (the front of the vehicle body) relative to the vertical direction.A secondary balancer system 16 fixed to a lower face of the lower block14 and housed within the oil pan 15 includes a driven balancer shaft 18and a follower balancer shaft 19, which are supported in a balancerhousing 17. A sprocket 21 provided at a shaft end of the crankshaft 20,which is supported between the cylinder block 13 and the lower block 14,is connected via an endless chain 23 to a sprocket 22 provided at ashaft end of the driven balancer shaft 18.

As shown in FIG. 2 to FIG. 5, four pistons 25 are slidably fitted infour cylinder bores 24 provided in the cylinder block 13, and areconnected to four pins 20 a of the crankshaft 20 via connecting rods 26.Five bearing caps 27 are fitted within the lower block 14 and are eachsecured to a lower face of the cylinder block 13 via two bolts 28. Fivejournals 20 b of the crankshaft 20 are rotatably supported between thecylinder block 13 and the five bearing caps 27.

The balancer housing 17 of the secondary balancer system 16 is formed byjoining an upper housing 29 and a lower housing 30 via eleven bolts 31,32, 34 a, and 34 b, and further joining a pump housing 35 to endportions of the upper housing 29 and the lower housing 30 via aplurality of bolts 36. An upper wall portion 30 b is formed in an endportion of the lower housing 30 on the pump housing 35 side so as toextend over an upper face side of the balancer housing 17, and thisupper wall portion 30 b is sandwiched between the upper housing 29 andthe pump housing 35. A slit-shaped opening a (FIG. 6, FIG. 8, and FIG.9) is formed between the upper housing 29 and the upper wall portion 30b of the lower housing 30.

The three bolts 31 disposed so as to sandwich the driven balancer shaft18 and the follower balancer shaft 19 therebetween are inserted from theupper housing 29 side and secured to the lower housing 30. The two bolts32 disposed outside the driven balancer shaft 18 and the two bolts 31disposed outside the follower balancer shaft 19 are inserted from theupper housing 29 side and secured to the lower housing 30. The two bolts34 a inserted into the pump housing 35 at one end of the balancerhousing 17 run through one of the bearing caps 27 and are secured to thelower face of the cylinder block 13, and the two bolts 34 b insertedfrom the lower housing 30 side at the other end of the balancer housing17 run through the upper housing 29 and one of the bearing caps 27 andare secured to the lower face of the cylinder block 13.

The upper housing 29 is supported on the bearing caps 27 via four mounts29 a through which the four bolts 34 a and 34 b run, thereby forming agap β (see FIG. 4) between an upper face of the upper housing 29 andlower faces of the bearing caps 27.

The structure of the secondary balancer system 16 is now explainedfurther with reference to FIG. 6 to FIG. 13.

As is clear from FIG. 8, the driven balancer shaft 18 of the secondarybalancer system 16 is provided with, going from one end to the other,the sprocket 22, a first journal 18 a, a driven gear 18 b, a firstbalancer weight 18 c, a second journal 18 d, and a second balancerweight 18 e. The first and second journals 18 a and 18 d are sandwichedand supported between the upper housing 29 and the lower housing 30. Asis clear from FIG. 9, the follower balancer shaft 19 of the secondarybalancer system 16 is provided with, going from one end to the other, afirst journal 19 a, a follower gear 19 b, a first balancer weight 19 c,a second journal 19 d, and a second balancer weight 19 e. The first andsecond journals 19 a and 19 d are sandwiched and supported between theupper housing 29 and the lower housing 30.

An oil pump 41 (see FIG. 9) is provided at the one end of the followerbalancer shaft 19, which projects into the interior of the pump housing35. The oil pump 41 is a known trochoidal pump, and includes an innerrotor 42 fixed to the follower balancer shaft 19 and an outer rotor 43rotatably supported by the pump housing 35 and meshing with the innerrotor 42. A strainer 44 is provided on a lower face of the lower housing30 at a position below an oil level O of oil that is held in the oil pan15, and the strainer 44 is connected to a suction port 41 a of the oilpump 41 via an oil passage 30 a (see FIG. 12) formed integrally with thelower face of the lower housing 30. The strainer 44 is formed from astrainer element 44 a for filtering out foreign matter in the oil and astrainer cover 44 b covering the strainer element 44 a. A discharge port41 b of the oil pump 41 is connected to a main gallery 13 a (see FIG. 3and FIG. 4) of the cylinder block 13 via an oil passage (notillustrated).

Formed in the upper housing 29 are a pair of openings 29 b facing thedriven gear 18 b and the follower gear 19 b, a pair of openings 29 cfacing the first balancer weights 18 c and 19 c, and a pair of openings29 d facing the second balancer weights 18 e and 19 e. By providingthese openings 29 b, 29 c, and 29 d it is possible to prevent atrajectory T (see FIG. 3) of the lower end of the connecting rods 26from interfering with an upper face of the upper housing 29, thusenabling the engine E to be reduced in size. Formed on an end face ofthe balancer housing 17 on the side opposite to the pump housing 35 areopenings 17 a and 17 b (see FIG. 10) facing shaft ends of the drivenbalancer shaft 18 and the follower balancer shaft 19, the openings 17 aand 17 b extending over the upper housing 29 and the lower housing 30.These openings 17 a and 17 b are used when machining the interior of thebalancer housing 17 so as to form supports for the first and secondjournals 18 a, 19 a, 18 d, and 19 d of the driven balancer shaft 18 andthe follower balancer shaft 19. The inner diameters of the openings 17 aand 17 b are slightly larger than outer diameters of the first andsecond journals 18 a, 19 a, 18 d, and 19 d.

Four oil discharge holes 45 a to 45 d are formed in an end portion ofthe upper housing 29 on the driven balancer shaft 18 side, the four oildischarge holes 45 a to 45 d opening on an upper face of the upperhousing 29. Each of the oil discharge holes 45 a to 45 d is formed in anelongated shape extending along the axial direction of the crankshaft20. One (or a plurality of) slit-shaped oil discharge hole 46 is formedin the end of the balancer housing 17 on the follower balancer shaft 19side, the slit-shaped oil discharge hole 46 extending along mating facesof the upper housing 29 and the lower housing 30. The oil dischargeholes 45 a to 45 d open in the direction of the cylinder axis L, and theoil discharge hole 46 opens in a direction orthogonal to the cylinderaxis L. Because of the inclination of the cylinder axis L, the balancerhousing 17 is inclined so that the driven balancer shaft 18 side (frontside of the vehicle body) is low and the follower balancer shaft 19 side(rear side of the vehicle body) is high, but the oil discharge holes 45a to 45 d on the driven balancer shaft 18 side and the oil dischargehole 46 on the follower balancer shaft 19 side are disposed at positionshigher than the horizontal oil level O (see FIG. 3) of the oil that isheld in the oil pan 15.

A substantially rectangular first baffle plate 47 is secured to an upperface of the end of the upper housing 29 on the driven balancer shaft 18side via the two bolts 32, which also join the upper housing 29 and thelower housing 30. A substantially rectangular second baffle plate 48 isfixed via two bolts 33 to a bank-shaped boss 30 c projectingly providedon an outer wall of the lower housing 30. The second baffle plate 48extends upward and rearward along the outer wall of the lower housing30, and its upper end reaches a position higher than the upper end ofthe oil discharge hole 46. A large number of through holes 30 d (seeFIG. 12 and FIG. 13) are formed in the bank-shaped boss 30 c, thethrough holes 30 d providing communication between an upper face and alower face of the bank-shaped boss 30 c. A rectangular U-shaped thirdbaffle plate 49 is fixed to the lower face of the lower block 14 viafour bolts 50.

When the engine E is running, rotation of the crankshaft 20 istransmitted to the driven balancer shaft 18 via the sprocket 21, theendless chain 23, and the sprocket 22, and rotation of the drivenbalancer shaft 18 is transmitted to the follower balancer shaft 19 viathe driven gear 18 b and the follower gear 19 b. Since the number ofteeth of the sprocket 21 of the crankshaft 20 is set so as to be twicethe number of teeth of the sprocket 22 of the driven balancer shaft 18,and the number of teeth of the driven gear 18 b is set so as to be equalto the number of teeth of the follower gear 19 b, the driven balancershaft 18 and the follower balancer shaft 19 rotate in oppositedirections to each other (see arrows A and B in FIG. 11 and FIG. 12) ata rotational speed that is twice the rotational speed of the crankshaft20, and secondary vibration of the engine E is damped by the first andsecond balancer weights 18 c, 19 c, 18 e, and 19 e provided on thedriven balancer shaft 18 and the follower balancer shaft 19.

While the engine E is running, since the crankshaft 20 splashes oilwithin the crankcase, the oil attempts to penetrate into the interior ofthe balancer housing 17 via the openings 29 b, 29 c, 29 d, 17 a, and 17b. When the oil penetrates into the interior of the balancer housing 17,the oil is stirred by the driven gear 18 b, the follower gear 19 b, thefirst and second balancer weights 18 c, 19 c, 18 e, and 19 e, etc. andthere is the problem that the stirring resistance increases. Bydischarging, via the oil discharge holes 45 a to 45 d and 46 of thebalancer housing 17, the oil swept up by the driven gear 18 b, thefollower gear 19 b, the first and second balancer weights 18 c, 19 c, 18e, and 19 e, etc. of the driven balancer shaft 18 and the followerbalancer shaft 19 rotating in the directions of arrows A and B in FIG.11 so as to return it to the oil pan 15, an increase in the stirringresistance is prevented.

During this process, as shown in FIG. 10 to FIG. 12, since outer edgesof the first and second baffle plates 47 and 48 and outer edges of coverportions 49 a and 49 b of the third baffle plate 49 are bent downward,the oil discharged via the oil discharge holes 45 a to 45 d and 46 isdiverted downward and the oil can be returned smoothly to the oil pan15.

The first baffle plate 47 and the second baffle plate 48 fixed to thebalancer housing 17 and the third baffle plate 49 fixed to the lowerblock 14 prevent the oil level O of oil that resides within the oil pan15 from being disturbed. Since at least portions of the first and thirdbaffle plates 47 and 49 extend to positions that cover the oil dischargeholes 45 a to 45 d of the balancer housing 17, when droplets of the oilsplashed accompanying rotation of the crankshaft 20 are scattered withinthe crankcase, the droplets of oil are blocked by the first and thirdbaffle plates 47 and 49, and it is thus possible to suppress theirpenetration into the interior of the balancer housing 17 via the oildischarge holes 45 a to 45 d. In this way, since the oil discharge holes45 a to 45 d are covered by utilizing the existing first and thirdbaffle plates 47 and 49, it is unnecessary to employ a special covermember for covering these oil discharge holes 45 a to 45 d, thusreducing the number of components and the number of assembly steps.

In particular, since the third baffle plate 49, which is rectangularU-shaped, is provided with a plurality of cover portions 49 a and 49 b,which cover the oil discharge hole 45 d and a part of the oil dischargehole 46, and with a cutout 49 c between the cover portions 49 a and 49b, the cutout 49 c makes it possible to minimize any increase in weightof the third baffle plate 49 while enabling the oil discharge hole 45 dand the part of the oil discharge hole 46 to be covered by the coverportions 49 a and 49 b. Moreover, since two of the four bolts 50 forfixing the third baffle plate 49 to the lower block 14 are disposed atpositions closer to the cover portions 49 a and 49 b than to the cutout49 c, it is possible to increase the rigidity of the cover portions 49 aand 49 b and suppress vibration. Furthermore, since the cutout 49 c isprovided at a position where it faces the second balancer weights 18 eand 19 e, which have a larger diameter than that of the second journals18 d and 19 d of the driven balancer shaft 18 and the follower balancershaft 19, it is possible to minimize any increase in the verticaldimension of the engine E.

Since the first baffle plate 47 in the role of a cover member covers theoil discharge holes 45 a to 45 c, which are a plurality of openings, andthe third baffle plate 49 in the role of a cover member covers the oildischarge holes 45 d and 46, which are a plurality of openings, that is,a plurality of openings are covered by a single cover member in eachcase, it is possible to reduce the number of cover members.

Since the first baffle plate 47 and the third baffle plate 49, whichcover the oil discharge holes 45 c and 45 d respectively provided to theside (in a direction orthogonal to the driven balancer shaft 18) of thefirst balancer weight 18 c and the second balancer weight 18 e providedon either side of the second journal 18 d, are provided independently asseparate bodies, it is possible to suppress any increase in thedimensions of the first and third baffle plates 47 and 49 as covermembers while avoiding a complicated arrangement for the connection ofthe first baffle plate 47 and the third baffle plate 49 in the areaaround the second journal 18 d.

Moreover, since the cylinder axis L is inclined toward the front of thevehicle body so that the front side of the balancer housing 17 is lowand the rear side thereof is high, it is easy for oil to flow into theinterior of the balancer housing 17 via the front side oil dischargeholes 45 a to 45 d, but since the front side oil discharge holes 45 a to45 d are formed at positions higher than the mating faces P of the upperhousing 29 and the lower housing 30, that is, formed so as to runthrough an upper wall of the upper housing 29, it is possible to preventeffectively the inflow of oil via the oil discharge holes 45 a to 45 d.On the other hand, since the rear side oil discharge hole 46 is at ahigh position, even when the oil discharge hole 46 is formed in themating faces P of the upper housing 29 and the lower housing 30, thussimplifying the structure, there is no possibility of a large amount ofoil flowing in therethrough.

As is clear from FIG. 12, an angle θ1, which is formed between the lowerhousing 30 and the mating faces P of the upper housing 29 and the lowerhousing 30 on the side (the rear side of the vehicle body) where thebalancer housing 17 is high, is smaller than an angle θ2, which isformed between the lower housing 30 and the mating faces P on the side(the front side of the vehicle body) where the balancer housing 17 islow. That is, the inclination of an inner face of the lower housing 30is shallow on the rear side of the vehicle body where it is difficultfor oil to be discharged because the position of the oil discharge hole46 is high, and in contrast the inclination of the inner face of thelower housing 30 is steep on the front side of the vehicle body where itis easy for oil to be discharged because the position of the oildischarge hole 46 is low. Therefore, when the oil level is inclined fromthe normal position O to a position O′ during forward acceleration ofthe vehicle, it is also possible to discharge effectively oil that iswithin the balancer housing 17 via the oil discharge hole 46, which isat a high position on the rear side of the vehicle body.

Moreover, since the inclination of the lower housing 30 is steep on theside where the balancer housing 17 is low (the front side of the vehiclebody), it is possible to contribute to a reduction in the dimensions ofthe balancer housing 17 by bringing the lower housing 30 closer to thedriven balancer shaft 18 in that area.

Furthermore, since the upper end of the second baffle plate 48 reaches aposition higher than the upper end of the oil discharge hole 46, evenwhen the oil level within the oil pan 15 is disturbed, it is possible toprevent oil from penetrating into the interior of the balancer housing17 via the oil discharge hole 46. Furthermore, even when oil flows inbetween the outer wall of the lower housing 30 and the second baffleplate 48, the oil can be returned to the oil pan 15 via the throughholes 30 d formed in the boss 30 c of the lower housing 30.

A second embodiment of the present invention is now explained withreference to FIG. 14.

In the first embodiment shown in FIG. 13, the second baffle plate 48 isfixed to the one bank-shaped boss 30 c provided on the outer wall of thelower housing 30 via the bolts 33, but in the second embodiment a secondbaffle plate 48 is fixed, via bolts 33, to two bosses 30 c provided onan outer wall of a lower housing 30, the two bosses 30 c being separatedfrom each other. A gap δ is therefore formed between the two bosses 30c, the outer wall of the lower housing 30, and the second baffle plate48. Oil that has flowed in between the outer wall of the lower housing30 and the second baffle plate 48 is returned to the oil pan 15 via thegap δ.

A third embodiment of the present invention is now explained withreference to FIG. 15.

As is clear from comparing FIG. 15 with FIG. 3 (the first embodiment),in the third embodiment a driven balancer shaft 18 side of a balancerhousing 17 faces the rear of a vehicle body, and a follower balancershaft 19 side thereof faces the front of the vehicle body. Therefore,even when the oil level on the driven balancer shaft 18 side risesduring forward acceleration of the vehicle, since oil discharge holes 45a to 45 d on the driven balancer shaft 18 side are formed in an upperface of the balancer housing 17, it is difficult for oil to penetrateinto the interior of the balancer housing 17 via the oil discharge holes45 a to 45 d, and it is possible to suppress degradation of the forwardacceleration performance of the vehicle. If the oil discharge holes 45 ato 45 d on the low side of the balancer housing 17 are provided atpositions higher than mating faces on the high side of the balancerhousing 17, degradation of the forward acceleration performance of thevehicle is yet further advantageously suppressed.

A fourth embodiment of the present invention is now explained withreference to FIG. 16 to FIG. 19.

As is clear from a comparison of FIG. 6 and FIG. 11 (the firstembodiment) with FIG. 16 and FIG. 17 (the fourth embodiment), whereasthe second baffle plate 48 of the first embodiment is fixed via the twobolts 33 to the bank-shaped boss 30 c projectingly provided on the outerwall of the lower housing 30, a second baffle plate 48 of the fourthembodiment is secured to an upper face of the end on a follower balancershaft 19 side of an upper housing 29 via two bolts 33, which also jointhe upper housing 29 and a lower housing 30.

A first baffle plate 47 and the second baffle plate 48 fixed to abalancer housing 17 and a third baffle plate 49 fixed to a lower block14 prevent an oil level O of oil held within an oil pan 15 from beingdisturbed. Since at least parts of the first to the third baffle plates47 to 49 extend to positions where they cover oil discharge holes 45 ato 45 d and 46 of the balancer housing 17, when droplets of oil splashedaccompanying rotation of a crankshaft 20 are scattered within acrankcase, the droplets of oil are blocked by the first to the thirdbaffle plates 47 to 49, and it is thus possible to suppress theirpenetration into the interior of the balancer housing 17 via the oildischarge holes 45 a to 45 d and 46. In this way, since the oildischarge holes 45 a to 45 d and 46 are covered by utilizing theexisting first to third baffle plates 47, 48, and 49, it is unnecessaryto employ a special cover member for covering these oil discharge holes45 a to 45 d and 46, thus reducing the number of components and thenumber of assembly steps.

Formed in a cylinder block 13 and the lower block 14 are two oil returnpassages 13 b and two oil return passages 14 a for returning to the oilpan 15 oil that has lubricated a valve operating mechanism, etc. withina cylinder head 12. An oil outlet 14 b at the lower end of one of theoil return passages 14 a of the lower block 14 faces a cutout-shapedescape section 47 a formed by indenting the outer edge of the firstbaffle plate 47 in a semicircular shape. An oil outlet 14 b at the lowerend of the other oil return passage 14 a of the lower block 14 faces acutout-shaped escape section 49 d formed by indenting the outer edge ofthe third baffle plate 49 in a semicircular shape. Since the escapesections 47 a and 49 d are cutout-shaped and are formed by indenting ina semicircular shape, the molding thereof is easy. Reference numerals 13c and 14 c in FIG. 19 denote a breather passage.

As is most clearly shown in FIG. 17, since the oil outlet 14 b of theone of the oil return passages 14 a is at a position that is offset fromthe oil discharge holes 45 a and 45 b that are the closest thereto, theoil outlet 14 b of the other oil return passage 14 a is at a positionthat is offset from the oil discharge hole 45 d that is the closestthereto and, moreover, these oil discharge holes 45 a, 45 b, and 45 dare covered by the first and third baffle plates 47 and 49, it ispossible to prevent effectively the oil that has dropped via the oiloutlets 14 b from flowing into the interior of the balancer housing 17via the oil discharge holes 45 a, 45 b, and 45 d.

Since the oil outlets 14 b of the oil return passages 14 a arepositioned so as to avoid the first and third baffle plates 47 and 49,that is, the oil outlets 14 b face the escape sections 47 a and 49 d ofthe first and third baffle plates 47 and 49, it is possible, withoutmaking the first and third baffle plates 47 and 49 especially compact,to smoothly return to the oil pan 15 oil that has been discharged viathe oil outlets 14 b while suppressing interference from the first andthird baffle plates 47 and 49. Moreover, since outer edges of the firstand third baffle plates 47 and 49, which include positions surroundingthe escape sections 47 a and 49 d, are bent downward, it is possible toyet more smoothly return to the oil pan 15 oil discharged via the oiloutlets 14 b by guiding it downward.

Furthermore, since the escape section 47 a of the first baffle plate 47is formed between two bolts 32 via which the first baffle plate 47 isfixed to the balancer housing 17, even when fastening bosses for thebolts 32 are sufficiently thick, the fastening bosses do not projectinto the escape section 47 a, and the rigidity with which the firstbaffle plate 47 is secured can thereby be enhanced. Similarly, since theescape section 49 d of the third baffle plate 49 is formed between twobolts 50 via which the third baffle plate 49 is fixed to the lower block14, even when fastening bosses for the bolts 50 are sufficiently thick,the securing bosses do not project into the escape section 49 d, and therigidity with which the third baffle plate 49 is secured can thereby beenhanced.

As is clear from FIG. 17, since the innermost end p of the escapesection 47 a of the first baffle plate 47 is positioned between facingends of the two oil discharge holes 45 a and 45 b that are positionedclose to the escape section 47 a, it is possible to ensure that there isa minimum distance from the escape section 47 a to the two oil dischargeholes 45 a and 45 b, and it is thus possible to suppress the penetrationof oil from the oil outlet 14 b into the oil discharge holes 45 a and 45b. Furthermore, by increasing the distance between the two oil dischargeholes 45 a and 45 b and moving the positions of the facing end portionsthereof outside a width W of the escape section 47 a, the effect ofsuppressing the penetration of oil into the oil discharge holes 45 a and45 b can be further improved.

Embodiments of the present invention are explained in detail above, butthe present invention can be modified in a variety of ways withoutdeparting from the spirit and scope thereof.

For example, in the first to the fifth embodiments the first and secondbaffle plates 47 and 48 are fixed to the balancer housing 17 and thethird baffle plate 49 is fixed to the lower block 14, but the positionsat which they are mounted may be changed as appropriate.

Furthermore, in the fourth and fifth embodiments the escape sections 47a and 49 d of the first and third baffle plates 47 and 49 are cutouts,but they may be holes.

Moreover, in the fourth embodiment the diameter of the oil outlets 14 bis set so as to be smaller than that of the escape sections 47 a and 49d but, as in a fifth embodiment shown in FIG. 20, the diameter of oiloutlets 14 b may be set so as to be larger than that of escape sections47 a and 49 d, or parts of the oil outlets 14 b may be offset from theescape sections 47 a and 49 d.

Furthermore, the shape and the number of the oil discharge holes 45 a to45 d and 46 may be changed as appropriate.

INDUSTRIAL APPLICABILITY

As hereinbefore described, the present invention can be applied suitablyto an engine balancer system having a balancer housing formed by joiningan upper housing and a lower housing via mating faces, the balancerhousing being disposed so as to face an oil pan beneath a crankshaft ofan engine.

1. An engine balancer system having a balancer housing (17) formed byjoining an upper housing (29) and a lower housing (30) via mating faces(P), the balancer housing (17) being disposed so as to face an oil pan(15) beneath a crankshaft (20) of an engine (E), and the balancerhousing (17) being inclined so that the height of the mating faces (P)varies from one side to the other, wherein oil discharge holes (45 a to45 d, 46) for discharging oil that is within the balancer housing (17)are formed in the mating faces (P) on the higher side of the balancerhousing (17) and in the upper housing (29) above the mating faces (P) onthe lower side of the balancer housing (17).